We have frequent visits by geese, loons, and grebes but this is the first time I can recall seeing mergansers. At least on this lake. There as been a dozen or so on the lake for the past two weeks. The other unusual visitors this year (spring) have been swans. The mergansers are quiet and fun to watch as they fish.
Interesting comment about the swans. I remember the post you submitted of unusual swan sightings last year as well. Over the summer, I saw three pairs of swans on University Lake, when usually there is only one pair.
Common mergansers can be found in Anchorage year-round, collecting in tight flocks during winter. Mergansers dive for their food, and may mix with other diving ducks where there is open fresh water. Cheney Lake is stocked by the Alaska Department of Fish and Game, and likely provides healthy feeding opportunities before the ice forms.